1. Field of the Invention
The present invention relates to a method of determining ambient air temperature, and more specifically to a method of determining ambient air temperature outside a motor vehicle.
2. Background Art
Temperature sensors are used to measure the temperature of ambient air surrounding a motor vehicle. Such temperature sensors are often located where they may pick up heat from non-ambient heat sources, such as vehicle components like an engine or radiator. Heat from these non-ambient heat sources, as well as self-heating effects of the temperature sensor, may result in inaccurate ambient air temperature readings.
Previous strategies for determining ambient air temperature, such as that described in U.S. Pat. No. 4,770,543, simply ignored air temperature sensor readings at low vehicle speeds. Consequently, accurate temperature readings were not available when a vehicle was stationary or moving slowly. Moreover, such strategies yielded erroneous temperature readings during rapid temperature changes, such as when a vehicle was moved from a warm interior location to a cold exterior environment.
Before applicant's invention, there was a need for a method of more accurately determining ambient air temperature. In addition, there was a need for a method that accounts for the heating effects of non-ambient heat sources. Additionally, there was a need for a method that provides improved responsiveness to rapid temperature changes. In addition, there was a need for a method that could reduce the number of air temperature sensors used on a motor vehicle. Problems addressed by the prior art as noted above and other problems are addressed by applicant's invention as summarized below.